How these hours are computed
Each centre is described in its own time zone — 08:00 to 17:00 in London, 09:00 to 18:00 in Tokyo — rather than by a frozen UTC hour. Daylight-saving rules are applied centre by centre at calculation time.
That is why in March and October the gap between London and New York changes for a week or two: the two centres do not switch on the same Sunday, and Sydney switches the other way.
Weekends are removed: the market closes on Friday at the New York close and reopens on Sunday evening at the Sydney open. Sessions that would fall inside that gap are not shown.